Medications is 35% of the scored PTCE (the PTCB exam). Answer 10 exam style questions on antibiotics and anti-infectives and see exactly which concepts would cost you points on test day.
Start the 10 questions →A patient is prescribed vancomycin capsules by mouth for Clostridioides difficile infection. Why is the oral route used for this infection?
These questions cover indications: oral vancomycin, counseling points: antituberculosis drugs, boxed warnings: fluoroquinolones, indications: antifungals and drug classes: tetracyclines. Each one shows the correct answer and why every other option is wrong, so a miss tells you exactly what to review before the PTCE.
Prefer to read first? Every question from the practice set above, with the correct answer and why each wrong option is wrong.
Answer: C. Oral vancomycin is minimally absorbed, so it acts directly in the colon against C. difficile. For systemic infections such as MRSA bacteremia, vancomycin must be given IV.
Why not A: Oral vancomycin is poorly absorbed, so it is not used for bloodstream infections.
Why not B: Systemic MRSA infections need IV vancomycin. Oral doses do not reach the blood.
Why not D: Vancomycin is an antibiotic, not a probiotic product.
Exam tactic: Vancomycin by mouth = C. diff only. Vancomycin IV = systemic infections.
Answer: B. Isoniazid can deplete vitamin B6 and cause peripheral neuropathy (numbness, tingling in the hands and feet). Pyridoxine is commonly added to prevent it, especially in at-risk patients.
Why not A: Pyridoxine does not change isoniazid absorption.
Why not C: Orange body fluids come from rifampin, and B6 does not prevent them.
Why not D: Isoniazid's main organ concern is the liver, and B6 is not given for the kidneys.
Exam tactic: Isoniazid + B6 = nerve protection. Isoniazid also = liver monitoring.
Answer: D. Fluoroquinolones (-floxacin) have a boxed warning for tendinitis and tendon rupture, most often the Achilles tendon. Risk is higher in patients over 60, with corticosteroid use, or after transplant. The patient should stop activity and contact the prescriber.
Why not A: Kidney stones are not the fluoroquinolone boxed warning. Heel pain points to the Achilles tendon.
Why not B: Gout is linked to thiazide diuretics. The Achilles symptom fits fluoroquinolone tendon injury.
Why not C: DVT usually causes calf swelling, and it is not a fluoroquinolone boxed warning.
Exam tactic: -floxacin + heel or tendon pain = boxed warning. Refer immediately.
Answer: C. Oral terbinafine is an antifungal used for onychomycosis. Toenail infection is treated for about 12 weeks and fingernail infection for about 6 weeks, because nails grow slowly. Liver function is a known safety concern.
Why not A: Influenza is treated with antivirals such as oseltamivir over days, not weeks.
Why not B: Genital herpes is treated with antivirals such as valacyclovir.
Why not D: Terbinafine is an antifungal and does not treat bacterial infections.
Exam tactic: Long antifungal course (weeks) = nails. Terbinafine = onychomycosis.
Answer: A. Minocycline, doxycycline and tetracycline share the -cycline suffix. Tetracyclines are widely used for acne, and they bind calcium, iron and antacids and can cause photosensitivity.
Why not B: Macrolides include azithromycin and clarithromycin (-thromycin).
Why not C: Cephalosporins start with ceph- or cef-, such as cephalexin.
Why not D: Fluoroquinolones end in -floxacin, such as ciprofloxacin.
Exam tactic: -cycline = tetracycline class.
Answer: D. Nitrofurantoin can turn urine brown or dark yellow. This is expected and harmless. Nitrofurantoin is taken with food to improve absorption and reduce stomach upset.
Why not A: Black, tarry stools may signal GI bleeding and are not a harmless nitrofurantoin effect.
Why not B: Yellow-green halos are a sign of digoxin toxicity.
Why not C: Blue-gray skin is linked to drugs such as amiodarone or minocycline, not nitrofurantoin.
Exam tactic: Color changes: nitrofurantoin = brown urine, rifampin = orange-red fluids, phenazopyridine = orange urine.
Answer: B. Doxycycline can irritate or ulcerate the esophagus if a dose lodges there. Taking it with plenty of fluid and staying upright for a while afterward, rather than taking it right before lying down, reduces this risk.
Why not A: Milk and other calcium sources bind doxycycline and reduce absorption.
Why not C: Dairy binds doxycycline. Opening capsules is not the counseling point here.
Why not D: Dry swallowing raises the risk of the capsule lodging in the esophagus.
Exam tactic: Doxycycline: big glass of water, stay upright, no dairy near the dose.
Answer: B. A metallic or unpleasant taste is a very common side effect of metronidazole. It is harmless and resolves after therapy. Patients must also avoid alcohol during treatment and for at least 3 days afterward.
Why not A: Metronidazole does not commonly cause loss of smell or hearing.
Why not C: Tinnitus is classically linked to high-dose aspirin or aminoglycosides.
Why not D: Lip swelling suggests angioedema or allergy, not a typical metronidazole effect.
Exam tactic: Metronidazole: metallic taste + no alcohol.
Answer: D. Cephalexin is a first-generation cephalosporin. Cephalosporins usually start with ceph- or cef- (cefuroxime, cefdinir, ceftriaxone). They are beta-lactams related to penicillins.
Why not A: Penicillins end in -cillin. Cephalexin is a cephalosporin.
Why not B: Fluoroquinolones end in -floxacin. Cephalexin is not one.
Why not C: Tetracyclines end in -cycline. Cephalexin is not one.
Exam tactic: ceph-/cef- = cephalosporin.
Answer: A. Clindamycin's boxed warning covers Clostridioides difficile-associated diarrhea, which can range from mild diarrhea to fatal colitis and can start weeks after therapy ends. The patient needs prompt prescriber evaluation.
Why not B: Stevens-Johnson syndrome is a severe skin and mucous membrane reaction, not diarrhea.
Why not C: Tendon rupture is the fluoroquinolone boxed warning.
Why not D: Lactic acidosis is the metformin boxed warning.
Exam tactic: Clindamycin = C. diff boxed warning, even weeks after the last dose.
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